This invention relates to an electric connection box used to interconnect wire harnesses, for example.
One purpose of an electric connection box, such as a fuse box, a relay box, or a branch connection box, is to absorb a joint (branch connection) included in a wire harness.
For this reason, bus bars formed by pressing and bending a metal plate have been used conventionally as constituents of internal circuitry. Branch tabs (male terminals) can be formed integrally with the bus bar in an upstanding manner at desired positions of the bus bar, as for example at its end or at its intermediate portion, and the number of poles can be increased and decreased freely. However, it is not advisable to provide a number of tabs on each bus bar, because the adjacent bus bars interfere with each other, the arrangement of the bus bars becomes complicated, and the yield of stamping of the bus bars, as well as the density of arrangement of the bus bars, is lower.
In view of these deficiencies, the present applicant has proposed an electric connection box as shown in FIG. 3, which employs press-connecting terminals capable of press-connection to a bus bar. This electric connection box is the subject of copending, commonly assigned Application No. 07/534,564 now U.S. Pat. No. 5,011,417. The contents of that application are incorporated herein by reference.
In FIG. 3, a box shaped body of the electric connection box A is constituted by an upper case 1 and a lower case 2. A plurality of bus bars 3 and 3' are accommodated within the body. The bus bars 3' are wider, and have a greater current-carrying capacity than the bus bars 3.
Each bus bar has tabs 6 (6') directed upwardly or downwardly. Female-female relay terminals 7 (7') are attached to the tabs, and are led into a housing 4 of the upper case 1 (or the lower case 2) so as to form a connector insertion portion 4A for an external connector and a fuse insertion portion 4B. A bus bar 3.sub.1 has a bridge-like press-connecting piece 8 disposed in a plane perpendicular to a horizontal surface of the circuit of the bus bar. A press-connecting terminal 9 is connected to this piece 8.
As shown in FIG. 4 on an enlarged scale, the press-connecting terminal 9 is constituted by a base plate portion 10 defined by a U-shaped frame. Press-connecting portions 11, each having a U-shaped slot 12, are formed on one side of the base plate portion 10. A plurality of tabs 13 (four in the illustrated construction) project from the other side of the base plate portion 10. The opposite free ends of the base plate portion 10 are bent into an L-shape to form press-insertion pieces 14.
Bus bar-mounting grooves 20, arranged in a pattern corresponding to the pattern of arrangement of the plurality of the bus bars 3, are formed in the surface of the lower case 2. Terminal holders 15 for the press-connecting terminals 9 are formed on the surface of the lower case 2.
As shown in FIG. 4, the terminal holder 15 includes a seat 16 for receiving the base plate portion 10 of the press-connecting terminal 9, and a pair of bus bar guide walls 17 and 17 for holding the pair of press-connecting portions 11 and 11 therebetween. A bus bar guide groove 17a is vertically formed in the wall 17. At the lower side of the bottom of the housing 4, a seat 16, surrounding a tab insertion hole 5 (see FIG. 5), is constituted by a positioning projection 16a on which the U-shaped base plate portion 10 of the press-connecting terminal 9 is adapted to be fitted, and a surrounding wall 16b. A press-insertion groove 18 for the press-insertion pieces 14 is provided on one side of the surrounding wall 16b.
FIG. 5 shows a press-connection condition between the press-connecting piece 8 of the bus bar 3.sub.1 and the press-connecting terminal 9. More specifically, the branch tabs 13 of the press-connecting terminal 9 project through the tab insertion hole 5 of the seat 16 into the housing 4. The base plate portion 10 is inserted in the surrounding wall 16b, and the press-insertion pieces 14 are pressed into the press-insertion groove 18. In this manner, the terminal 9 is fitted in the terminal holder 15. In this condition, the press-connecting piece 8 of the bus bar 3 is inserted in the guide grooves 17a of the pair of bus bar guide walls 17.
When the upper case 1 is put on the lower case 2, the press-connecting piece 8 is press-fitted in and connected to the slots 12 of the press-connecting portions 11 by a pressing projection 19 of the upper case 1. In this manner, the base plate portion 10 and the press-connecting portions 11 of the press-connecting terminal 9 are held fixedly between the pressing projection 19 of the upper case 1 and the seat 16 of the lower case 2 from the upper and lower sides.
The electric connection box shown in FIGS. 3 to 5 is assembled as shown in FIGS. 6A-6D. In FIG. 6A, the press-connecting terminal 9 is attached to the terminal holder 5 on the lower case 2 as described above. In FIG. 6B, the press-connecting piece 8 of the bus bar 3.sub.1 is held by a chuck 21. Then, as shown in FIG. 6C, the piece 8 is inserted in the guide grooves 17a and 17a of the bus bar guide walls 17 and 17. In the final step shown in FIG. 6D, the upper case 1 is put on the lower case, so that the press-connecting piece 8 is urged by the pressing projection 19 and is press-connected to the press-connecting portions 11 (see FIG. 5).
However, there are occasions when the press-connecting piece 8 held by the chuck 21 in FIG. 6B is displaced right or left from its proper position relative to the bus bar 3 , as shown in FIG. 7A, or the height of the press-connecting piece 8 from the circuit surface of the bus bar 3 is displaced upwardly or downwardly from a proper height h, as shown in FIG. 7B. When such a precision defect is involved, the circuit surface of the bus bar 3 is affected, and therefore is not disposed in registry with its mating bus bar-mounting groove 20, as shown in FIG. 8. As a result, the tab 6 of each bus bar 3 having the press-connecting piece 8 is not in registry with the tab insertion hole 5 in the upper case 1 or the lower case 2, so that the final assembly in FIG. 6D cannot be carried out.